1. Field of the Invention
The present invention relates to a cable reel for an automotive steering device.
2. Description of the Related Art
Cable reels may be provided for electrical connections between steering columns and rotatable steering wheels. For example, a conventional cable reel is shown in FIGS. 4 and 5.
As shown in FIG. 4, a cable reel provides a movable electrical connection between a fixed housing 1, which is fixedly attached to a steering column, and a rotatable housing 2, which is fixedly attached to a rotatable steering wheel. Spiral-wound flat cable 3 resides in a circular space formed between an outer wall 1c of fixed housing 1 and an inner wall 2c of rotatable housing 2.
The ends of flat cable 3 are attached to bus bars 5 and 8 which are located within respective cable holders 4 and 7. Lead wires 6 and 9 extend from respective bus bars 5 and 8 to external circuits. Cable holder 4, which is attached to one end of flat cable 3, resides within rotatable housing space 2a, and cable holder 7, which is attached to the other end of flat cable 3, resides within fixed housing space 1a. 
As illustrated in FIG. 5, cable holder 4, which resides within rotatable housing 2, is an approximately L-shaped structure. Rib 2e, which is a plate-like member protruding from upper wall 2d of rotatable housing 2, presses inward on the external surface of cable holder end 4a from which flat cable 3 extends.
Because rotatable housing internal wall 2c is formed with a relatively small diameter in order to reduce the length of flat cable 3 to a minimum, rib 2e is only able to apply a limited amount of pressure as a result of its thin plate-like construction. When flat cable 3 unwinds from the rotation of rotatable housing 2, the bending of flat cable 3 in a direction opposite to the unwinding direction applies a load to the external side of cable holder end 4a. This load may cause rib 2e to bend or break, reducing the applied pressure below that required for flat cable 3 to be securely anchored within cable holder 4 in space 2a. 
Moreover, once cable holder end 4a bends in an outward direction from the load applied by an unwinding flat cable 3, a load is also applied to soldered connection A between flat cable 3 and bus bar 5, increasing the possibility of damaging the soldered connection.
The present invention has been made in view of the above-described problems. Accordingly, it is an object of the present invention to provide structure for a cable reel that can increase the pressure through which the flat cable is held within the cable holder, and thus better protect the soldered connection between the flat cable and bus bar when the flat cable attempts to bend in a direction opposite to the unwinding direction.
According to one aspect of the present invention, there is provided a cable reel including a fixed housing, a rotatable housing rotatably connected to the fixed housing, and a flat cable positioned within a space defined between the fixed housing and the rotatable housing. The cable reel also includes a cable holder positioned on one end of the flat cable, the cable holder containing a joint portion connecting conductor wires of the flat cable and a bus bar. The cable holder includes an end portion from which the flat cable extends, and the end portion includes a flange portion. The rotatable housing includes a cable holder space configured to contain the cable holder, and a rib member extending from a wall of the rotatable housing adjacent to the cable holder space. The rib member is configured such that a first surface of the rib member contacts the end portion of the cable holder, and a second surface of the rib member, which is substantially perpendicular to the first surface, contacts the flange portion.
When the rotatable housing turns in the cable unwinding direction, the flat cable attempts to fold back in a direction opposite to the unwinding direction. External pressure is applied to the end of the cable holder from which the flat cable extends, and the flange portion presses against the edge of the rib member. Because of its plate-like shape, the rib member tends to bend easily when a load is applied against its planar surface. However, the rib member is able to provide a high degree of rigidity due to a load being applied by the flange portion of the cable holder to the edge of the rib member in a direction substantially perpendicular to the rib member""s planar surface. The rib member is thus reinforced by the protruding flange portion contacting the edge of the rib member when the flat cable unwinds. This structure increases the grip of the case holder on the flat cable while preventing damage to the rib member. The cable holder structure is more resistant to bending, making it difficult for loads from the flat cable to reach the soldered joint that connects the flat cable to the bus bar. This reduces the chances of damaging the joint, and thereby increases the reliability of the electrical connection.
According to a further aspect of the present invention, the cable reel includes a guide flap extending from the end portion of the cable holder from which the flat cable extends. The guide flap may extend along a surface of the flat cable, including an inner surface. The guide flap may be bonded to a surface of the flat cable, including an inner surface. The guide flap may rigid, and inhibits bending of a portion of the flat cable adjacent to the cable holder.
The installation of a rigid or flexible guide flap, which extends from the end of the cable holder along the outer or inner surface of the flat cable, prevents the flat cable from folding back in a direction opposite to the cable unwinding direction. The guide flap may be made from a flexible or rigid synthetic resin, and the guide flap may be bonded to the flat cable.
According to a further aspect of the present invention, the fixed housing and the rotatable housing are substantially cylindrical, and the flat cable is wound in a predetermined direction within the space defined between the fixed housing and the rotatable housing.
According to a further aspect of the present invention, the first surface and the second surface of the rib member inhibit bending of the end portion of the cable holder in order to prevent damage to the joint portion and to maintain one end of the flat cable in the cable holder.
According to another aspect of the present invention, there is provided a cable reel in which a flat cable is positioned between a rotatable housing and a fixed housing. The cable reel includes a cable holder containing a joint portion connecting conductor wires of the flat cable and a bus bar, the cable holder including an end portion from which the flat cable extends. The cable reel also includes a cable holder mounting position on the rotatable housing and a rib member positioned on the rotatable housing adjacent to the cable holder mounting position. The rib member engages first and second substantially perpendicular surfaces of the end portion of the cable holder.
According to a further aspect of the present invention, the rib member includes first and second substantially perpendicular surfaces for respectively engaging the first and second substantially perpendicular surfaces of the end portion of the cable holder. The rib member inhibits bending of the end portion of the cable holder in order to prevent damage to the joint portion and to maintain one end of the flat cable in the cable holder.
According to a further aspect of the present invention, the cable reel includes a guide flap extending from the end portion of the cable holder from which the flat cable extends. The guide flap may extend along a surface of the flat cable, including an inner surface. The guide flap may be bonded to a surface of the flat cable, including an inner surface. The guide flap may rigid, and inhibits bending of a portion of the flat cable adjacent to the cable holder.